Fluorescence detection is widely used in biochemical and medical research applications due to its high sensitivity. For example, fluorescence detection is used in automated DNA sequencing, capillary electrophoresis and a variety of immunoassays. In response to excitation, fluorescent biomolecules and dyes emit light at characteristic wavelengths, which differ from the excitation wavelength. By detecting these characteristic wavelengths, the composition of a sample can be determined.
In many biological applications, the amount of sample to be detected is usually quite small. Over the years, methods and apparatus have been able to manipulate and separate on smaller and smaller scales, going from the μM range to nM and pM ranges. As the sample size decreases, the background fluorescence becomes more significant in relation to the fluorescence of the sample.
The dominant background noise source in fluorescence detectors is often shot noise. Shot noise comes from the sample and background fluorescence. The background fluorescence comes from fluorescence or Raman scattering from the sample as well as from the substrate that the sample is contained in. High background fluorescence also reduces the dynamic range of the detector by causing saturation of the detector. Therefore, reducing the background noise is one strategy for improving the performance of fluorescence detectors.